Mixers play an indispensable role in communication systems as frequency-translation devices for both down- and up-conversion. At microwave frequencies, monolithically integrated mixers using a single or multiple transistors exist in various semiconductor technologies such as Si bipolar, CMOS, SiGe HBT, GaAs FET, GaAs p-HEMT. Various circuit topologies are also in evidence, resulting in both passive and active type of mixers.
In addition to relatively moderate demand for conversion gain, high linearity and low noise figure are often required for these mixers. However, a common problem with existing mixer topologies is the difficulty to offer a combination of high linearity and low noise while still providing positive conversion gain.
Consequently, there is a need for mixer topologies that enable simultaneously high linearity, low noise and positive gain.